Optical pickup device and recording and/or reproducing apparatus for optical disc

ABSTRACT

An optical pick-up device used for recording and/or reproduction of at least two kinds of optical discs different in kind. This optical pick-up device comprises a first object lens, a second object lens having numerical aperture different from numerical aperture of the first object lens, a bobbin on which the first and second object lenses are attached, and a drive mechanism for moving the bobbin in a first direction in parallel to the optical axes of the first and second object lenses and in a second direction perpendicular to the optical axes of the first and second object lenses. Thus, such an approach is employed to selectively use the first and second object lenses to thereby carry out recording and/or reproduction of at least two kinds of optical discs different in kind.

TECHNICAL FIELD

This invention relates to an optical pick-up device and a recordingand/or reproducing apparatus for optical disc used for carrying outrecording and/or reproduction of information signals with respect to twokinds of optical discs different in kind, and more particularly to anoptical pick-up device and a recording and/or reproducing apparatus foroptical disc, which permit recording and/or reproduction of informationsignals with respect to two kinds of optical discs different in kind byselectively using first and second object lenses (objectives) attachedon a single bobbin.

BACKGROUND ART

Hitherto, as recording media for information signals such as soundsignals and/or video signals, and data, etc. processed at informationprocessing equipment such as computer, etc., various kinds of opticaldiscs have been used and have been proposed.

As the optical disc of this kind, there are used optical discs adaptedfor recording sound signals and/or data, etc. processed at informationprocessing equipment such as computer, etc., and having diameter causedto be 120 mm or 80 mm and thickness caused to be 1.2 mm. Such opticaldiscs are called Compact Disc (CD).

Moreover, there are also used video discs which are optical discsadapted for mainly recording video signals as information signal, andhaving diameter caused to be 300 mm or 200 mm and thickness caused to be1.2 mm.

Further, with realization of multi-media of information signals, therehas been demand for realization of wide variety and vast (gigantic)quantity of information signals such as picture data or sound data, etc.which are handled at a time. To satisfy such demand, as optical disc inwhich the medium itself has been miniaturized while realizing highrecording density, there have been proposed optical discs in which twooptical discs each having diameter caused to be 120 mm and thickness ofthe disc base (substrate) caused to be 0.6 mm are stuck to each other sothat the entire thickness is 1.2 mm, and optical discs in which opticaldisc having thickness of 0.6 mm and disc reinforced plate havingthickness of 0.6 mm are stuck to each other so that the entire thicknessis caused to be 1.2 mm. Such optical discs are generally called DigitalVideo Disc (DVD).

In general, the optical disc constituted as a recording medium forinformation signals are adapted as shown in FIG. 1 so that non-signalrecording areas 202, 203 are respectively provided at the innercircumferential side area of the outer periphery of a center hole 201formed at the central portion and the outermost circumferential sidearea, and a signal recording area 204 where information signals arerecorded is provided within the area encompassed by the innercircumferential side non-signal recording area 202 and the outercircumferential side non-signal recording area 203. At the innercircumferential side of the signal recording area 204, there is provideda TOC (Table of Contents) area 205 in which addresses of informationsignals recorded in the signal recording area and management informationsuch as table (of contents) of recording contents, etc. are recorded.Further, in the optical disc, in the state where the innermostcircumferential side position of the TOC area is caused to be readstarting position of information signals, i.e., lead-in position, readoperation of information signals recorded on the optical disc is startedfrom the lead-in position. In addition, in CD 210 having diameter causedto be 120 mm, the lead-in position is set at the position where radiusR₁ from the disc center O₁ is 23 mm.

In order to carry out read operation of information signals recorded onthis optical disc, the optical pick-up device is caused to be movedtoward the innermost circumferential side position of the optical disc.At this time, the object lens (objective) which focuses light beamsemitted from the light source of the optical pick-up device to irradiatethem onto the optical disc is adapted so that its optical axis is causedto be in correspondence with the lead-in position. In addition, when thelead-in position which serves as reference position of read starting ofinformation signals is caused to undergo movement operation toward theouter circumferential side of the optical disc, the optical pick-updevice scans the signal recording area of the optical disc by lightbeams emitted from the light source to carry out read operation ofinformation signals.

Meanwhile, in the recording and/or reproducing apparatuses for opticaldisc using optical disc as recording medium, there have been proposedapparatuses adapted for reproducing, by using the same optical pick-updevice, information signals recorded on optical discs of pluralspecifications in which their lead-in positions are different from eachother.

As the recording and/or reproducing apparatus for optical disc of thiskind, there are used optical disc recording and/or reproducingapparatuses capable of reproducing, with compatibility, CDs and videodiscs in which their lead-in positions are different from each other. Insuch optical disc recording and/or reproducing apparatuses, attention isdrawn to the fact that diameters of the CD and the video disc aredifferent from each other to discriminate sizes of these optical discsby the discrimination mechanism to control the lead-in position of theoptical pick-up device in dependency upon its discrimination result tocarry out reproduction of information signals from lead-in positionscorresponding to respective optical discs.

In recording and/or reproducing apparatuses adapted to adjust (change)the lead-in position of the optical pick-up device in correspondencewith the specification of the optical disc used as stated above, themovement range of the optical pick-up device is caused to be broad ascompared to the size of the optical disc used. As a result, not only theapparatus itself becomes large-sized, but also feed control of theoptical pick-up device becomes complicated because the referenceposition of the optical pick-up device is changed.

Additionally, also in CD and DVD, lead-in positions of the opticalpick-up device are different from each other.

Moreover, in the recording and/or reproducing apparatuses for opticaldisc using optical disc as recording medium, there have been proposedapparatuses capable of using, with compatibility, optical discs in whichthicknesses of their disc substrates are different from each other,e.g., CD and DVD, and CD, DVD and video disc. When the thickness of theoptical disc is different, the distance from the object lens up to thesignal recording surface of the optical disc would be varied. In orderto use, with compatibility, optical discs of plural specifications inwhich their thicknesses are different from each other, plural objectlenses (objectives) having focal lengths (distances) different from eachother are required.

In optical pick-up devices provided with plural object lenses, pluralobject lens are caused to undergo rotational operation so that everytime each of optical discs different in thickness is loaded, the opticalaxis of object lense corresponding to each optical disc is positioned onthe center line of the loaded optical disc. However, when the mechanismfor allowing the object lenses to undergo rotational operation isprovided, the optical pick-up device becomes large-sized. When theoptical pick-up device becomes large-sized, the feed mechanism of theoptical pick-up device also becomes large-sized. As a result, theoptical disc recording and/or reproducing apparatus itself also becomeslarge-sized.

Moreover, in optical pick-up devices used in optical disc recordingand/or reproducing apparatuses capable of using, with compatibility,optical discs in which thicknesses of their disc bases are differentfrom each other, there have been also proposed optical pick-up devicesin which single object lens is used to adjust (vary), in dependency uponthickness of the optical disc to be loaded, distance of the object lenswith respect to the optical disc, i.e., the reference height positionwith respect to the optical disc of the object lens. However, in orderto change the reference height position of the object lens, themechanism for allowing the object lens to undergo adjustable driving inthe optical axis direction thereof becomes complicated. In addition, themechanism for displacably supporting the object lens in the optical axisdirection thereof becomes complicated.

DISCLOSURE OF THE INVENTION

An object of this invention is to provide a novel optical pick-up deviceused for recording and/or reproduction of plural optical discs differentin size.

Another object of this invention is to provide a novel optical pick-updevice and a recording and/or reproducing apparatus for optical discused for recording and/or reproduction of plural optical discs differentin thickness.

A further object of this invention is to provide an optical pick-updevice and a recording and/or reproducing apparatus for optical disc,which realize miniaturization and light weight of the entirety of thedevice and the apparatus.

A still further object of this invention is to provide an opticalpick-up device and a recording and/or reproducing apparatus for opticaldisc, which can easily carry out feed control to the reference positionwith respect to the optical disc, and can simplify the mechanism forcarrying out feed control.

An optical pick-up device for recording and/or reproduction of opticaldisc, which is proposed in order to attain such objects, comprises afirst object lens and a second object lens, wherein the first and secondobject lenses are attached on a bobbin in such a manner that respectiveoptical axes are in parallel to each other, and that either one of thefirst and second object lenses is positioned on line passing through thecenter of the optical disc. The bobbin on which the first and secondobject lenses are attached is moved, by a drive mechanism, in a firstdirection in parallel to the optical axes of the first and second objectlenses and in a second direction perpendicular to the optical axes ofthe first and second object lenses.

The object lens disposed on the line passing through the center of theoptical disc of the first and second object lenses is attached on thebobbin so that when this object lens is positioned at the innermostcircumference of the optical disc, it is located at a read startingposition of the optical disc, whereby switching of at least the objectlens is not required for the optical disc where the first object lens isused (applied).

Moreover, the first and second object lenses are attached on the bobbinin such a manner that when one object lens disposed on the line passingthrough the center of the optical disc thereof is located at the readstarting position of one optical disc, the other object lens is locatedat the read starting position of the other optical disc, whereby theread starting position is fixed also with respect to either opticaldisc. Thus, movement control to the read starting position isfacilitated.

Further, the first and second object lenses are attached on the bobbinalong the tangential line direction of tracks of the optical disc,thereby making it possible to precisely carry out correct trackingcontrol with respect to either optical disc.

The drive mechanism for moving the bobbin in the first direction inparallel to the optical axes of the first and second object lenses andin the second direction perpendicular to the optical axes of the firstand second object lenses is of a structure comprising at least oneelastic supporting member for movably supporting the bobbin in the firstand second directions, a fixed portion on which the end portion of theelastic supporting member is attached, plural coils provided at eitherone of the bobbin and the fixed portion, and at least one magnetprovided at the other and opposite to the plural coils, thus making itpossible to move, by simple configuration, the first and second objectlenses in the direction in parallel to the optical axes thereof and inthe direction perpendicular to the optical axes thereof.

The optical pick-up device according to this invention further comprisesa first light source, a first optical system for guiding light beamsfrom the first light source to the first object lens, a second lightsource for emitting light beams having wavelength different fromwavelength of light beams emitted from the first light source, and asecond optical system for guiding light beams from the second lightsource to the second object lens, thus making it possible to carry outrecording and/or reproduction of information signals with respect toplural kinds of optical discs different in recording density.

Further, since the numerical aperture of the first object lens and thenumerical aperture of the second object lens are different from eachother, it is possible to carry out recording and/or reproduction ofinformation signals with respect to plural kinds of optical discsdifferent in distance from the object lens.

Furthermore, the first and second object lenses are attached on thebobbin so that they are respectively positioned on line passing throughthe center of the optical disc, thus permitting the optical axis of theobject lens to be positioned on line passing through the center of theoptical disc even with respect to plural kinds of optical discsdifferent in the specification. As a result, it is possible to carry outrecording and/or reproduction of information signals, with satisfactoryrecording/reproduction characteristic, also with respect to eitheroptical disc.

Further, an optical pick-up device according to this invention used inrecording and/or reproduction of at least two kinds of optical discsdifferent in kind comprises a first object lens, a second object lenshaving numerical aperture different from numerical aperture of the firstobject lens, a bobbin attached in such a manner that respective opticalaxes of the first and second object lenses are in parallel to eachother, and at least one of the first and second object lenses is locatedat the recording starting position of the optical disc when the opticalpick-up device is positioned at the innermost circumference of theoptical disc, and a drive mechanism for moving the bobbin in a firstdirection in parallel to the optical axes of the first and second objectlenses and in a second direction perpendicular to the optical axes.

Further, an optical pick-up device according to this invention used inrecording and/or reproduction of at least two kinds of optical discshaving thicknesses different from each other comprises a first objectlens for irradiating light beams from a first light source onto eitherone of two kinds of optical discs, a second object lens for irradiatinglight beams from a second light source onto the other of the two kindsof optical discs, a bobbin attached in such a manner that respectiveoptical axes of the first and second object lenses are in parallel toeach other and either one of the first and second object lenses isdisposed on line passing through the center of the optical disc, and adrive mechanism for moving the bobbin in a first direction in parallelto the optical axes of the first and second object lenses and in asecond direction perpendicular to the optical axes of the first andsecond object lenses.

Furthermore, a recording and/or reproducing apparatus for optical discaccording to this invention for carrying out recording and/orreproduction of at least two kinds of optical discs having thicknessesdifferent from each other comprises an optical pick-up device comprisinga first object lens for irradiating light beams from a first lightsource onto either one of two kinds of optical discs, a second objectlens for irradiating light beams from a second light source onto eitherthe other of the two kinds of optical discs, a bobbin attached in such amanner that respective optical axes of the first and second objectlenses are in parallel to each other and either one of the first andsecond object lenses is positioned on line passing through the center ofthe optical disc, and a drive mechanism for moving the bobbin in a firstdirection in parallel to the optical axes of the first and second objectlenses and in a second direction perpendicular to the optical axes, andfurther comprises a discrimination mechanism for discriminating kind ofoptical disc loaded within the recording and/or reproducing apparatus tocarry out switching between the first light source and the second lightsource on the basis of the discrimination result, thus to switch thelight source used in dependency upon kind of optical disc loaded.

Still more further objects of this invention and more practical meritsobtained by this invention will become more clear from the descriptionof embodiments which will be given below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing signal recording area and recordingstarting position of information signal of optical disc used in (appliedto) an optical pick-up device according to this invention.

FIG. 2 is a plan view showing an optical pick-up device according to afirst embodiment of this invention and an optical disc recording and/orreproducing apparatus using this optical pick-up device.

FIG. 3 is a plan view showing the optical pick-up device according tothe first embodiment of this invention.

FIG. 4 is a plan view showing positions (positional relationship) withrespect to first and second optical discs of optical axes of first andsecond object lenses constituting the optical pick-up device.

FIG. 5 is a plan view showing an optical pick-up device according to asecond embodiment of this invention and an optical disc recording and/orreproducing apparatus using this optical pick-up device.

FIG. 6 is a plan view showing the optical pick-up device according tothe second embodiment of this invention.

FIG. 7 is a plan view showing an optical pick-up device according to athird embodiment of this invention.

FIG. 8 is a plan view showing an optical pick-up device according to afourth embodiment of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An optical pick-up device and a recording and/or reproducing apparatusfor optical disc according to this invention will now be described withreference to the attached drawings.

A first embodiment of the optical pick-up device and the optical discrecording and/or reproducing apparatus using such optical pick-up deviceaccording to this invention will be described below.

The optical pick-up device disclosed here is used for recording and/orreproduction of Compact Disc (CD) which is a first optical disc 210having diameter caused to be 120 mm and thickness caused to be 1.2 mm,and adapted so that sound signals are mainly recorded, and Digital VideoDisc (DVD) which is a second optical disc 211 in which two optical discseach having diameter caused to be 120 mm and the thickness of the discbase caused to be 0.6 mm are stuck to each other so that the entirethickness is caused to be 1.2 mm, and adapted so that informationsignals such as video signals, etc. are mainly recorded at higherdensity as compared to the first optical disc 210.

In the CD in which the optical pick-up device according to thisinvention is used (applied), i.e., the first optical disc 210, aspreviously mentioned FIG. 1, the lead-in position which is the readstarting position of information signals is set to the position whereradius R₁ from the disc center O₁ is 23 mm. Moreover, in the DVD inwhich the optical pick-up device according to this invention is used(applied), i.e., the second optical disc 211, the lead-in position isset to the position where radius R₁ from the disc center O₁ is 22.6 mm.Namely, this optical pick-up device 1 is used for recording and/orreproduction of information signals with respect to the first opticaldisc 210 and the second optical disc 211 in which their lead-inpositions are different from each other.

The optical pick-up device 1 of the first embodiment is used, e.g., inthe optical disc recording and/or reproducing apparatus using theabove-described first and second optical discs 210, 211 as recordingmedium, and is disposed as shown in FIG. 2 within the optical discrecording and/or reproducing apparatus through a base 3 constituting theapparatus body. On this base 3, the first or second optical disc 210 or211 is loaded, and a disc rotational operation mechanism composed of adisc table 4 for allowing these optical discs 210, 211 to selectivelyundergo rotational operation and spindle motor for allowing this disctable 4 to undergo rotational drive is disposed. The spindle motorconstituting this disc rotational operation mechanism is attached at thelower surface side of the base 3.

Moreover, on the base 3, a guide shaft 5a and a drive shaft 5b aredisposed in parallel to each other in such a manner that the disc table4 is put therebetween. The optical pick-up device 1 is movably supportedin the radial direction of the first or second optical disc 210 or 211loaded on the disc table 4 by allowing both ends of an optical block 6including therewithin light detector (photo-detector) for detectinglight beams from semiconductor laser serving as light source or lightbeams reflected from the first or second optical disc 210, 211 to carryout read operation of information signals recorded on these opticaldiscs 210, 211 and optical parts such as beam splitter, etc. to besupported by the guide shaft 5a and the drive shaft 5b. Further, theoptical pick-up device 1 is adapted so that the drive shaft 5b is causedto undergo rotational drive by feed motor (not shown), whereby it iscaused to undergo feed operation in a direction indicated by arrow X₁and in a direction indicated by arrow X₂ in FIG. 2 which are trackingdirection extended in (along) the radial direction of the first orsecond optical disc 210, 211 loaded on the disc table 4 while beingguided by the guide shaft 5a.

In this example, in the case where the optical pick-up device 1 carriesout read-out operation of information signals recorded on the first orsecond optical disc 210, 211, it is caused to undergo feed operation inthe direction indicated by arrow X₁ in FIG. 2 from the lead-in positionprovided at the inner circumferential side of the first or secondoptical disc 210, 211 toward the outer circumferential side of the firstor second optical disc 210, 211.

This optical pick-up device 1 comprises, as shown in FIGS. 2 and 3, afirst object lens (objective) 7 used at the time of reading outinformation signals recorded on the first optical disc 210, a secondobject lens (objective) 8 used at the time of reading out informationsignals recorded on the second optical disc 211, and a bobbin 9 on whichthese first and second object lenses 7, 8 are attached. The first andsecond object lenses 7, 8 are attached on the bobbin 9 so thatrespective optical axes are in parallel to each other. Moreover, at theoptical pick-up 1, there is provided an electromagnetic drive mechanism10 for moving the bobbin 9 in the focusing direction which is the firstdirection in parallel to the optical axes of the first and second objectlenses 7, 8 and in the tracking direction which is the second directionperpendicular to the optical axes of the first and second object lenses7, 8.

Further, the first object lens 7 is attached on the bobbin 9 in such amanner that when the optical pick-up device 1 is moved to the innermostcircumferential side position with respect to the first or secondoptical disc 210, 211, the optical axis P₁ is located at lead-inposition 2a which is the read starting position of the first opticaldisc 210 as shown in FIG. 3. Further, the second object lens 8 isattached on the bobbin 9 in such a manner that when the optical pick-updevice 1 is moved to the inner most circumferential side position withrespect to the first or second optical disc 210 or 211, the optical axisP₂ is located at lead-in position 2b of the second optical disc 211 asshown in FIG. 3. Furthermore, the second object lens 8 is attached onthe bobbin 9 in such a manner that it is located on the center line S₁passing through the rotation center O₁ of the second optical disc 211loaded on the disc table 4. In addition, the first object lens 7 and thesecond object lens 8 are disposed at positions symmetrical with asupport shaft 11 for supporting this bobbin 9 which serves as center ofrotation of the bobbin 9 being as center.

Meanwhile, the bobbin 9 on which the first and second object lenses 7, 8are attached is formed substantially cylindrical so that it includes topplate, and is adapted so that the central portion thereof is supportedby the support shaft 11. In addition, the bobbin 9 is permitted to beslid in the axial direction of the support shaft 11 and is rotatablysupported in the direction around the axis of the support shaft 11. Inthis example, the bobbin 9 is held so that it is placed at the neutralposition by the neutral point supporting mechanism constituted by rubberhaving elasticity, or the like.

The bobbin 9 is caused to undergo drive displacement by theelectromagnetic drive mechanism 10, whereby it is slid in the axialdirection of the support shaft 11 and is further rotated in thedirection around the axis of the support shaft 11. Namely, the bobbin 9is caused to undergo slide displacement in the axial direction of thesupport shaft 11, whereby the first and second object lenses 7, 8 arecaused to undergo drive displacement in the first direction in parallelto their optical axes so that focusing control with respect to the firstor second optical disc 210, 211 is carried out. As a result, the bobbin9 is caused to undergo rotational displacement in the direction aroundthe axis of the support shaft 11. Thus, the first and second objectlenses 7, 8 are caused to undergo drive displacement in the seconddirection perpendicular to their optical axes so that tracking controlwith respect to the first or second optical disc 210 or 211 is carriedout.

The electromagnetic drive mechanism 10 for allowing the bobbin 9 toundergo drive displacement is composed, as shown in FIG. 3, of a magnetfor focusing and a yoke for focusing, and a magnet for tracking and ayoke for tracking which form a magnetic circuit 10a, and a coil 10b forfocusing and a coil 10c for tracking, whereby when focus error signal isdelivered to the focusing coil 10b, the electromagnetic drive mechanism10 allows the bobbin 9 to undergo drive displacement, and when trackingerror signal is delivered to the tracking coil 10c, it allows the bobbin9 to undergo rotational displacement in the direction around the axis ofthe support shaft 11.

Moreover, on the base 3, there is provided, although not shown, in amanner adjacent to the disc table 4, initial position detecting switchfor detecting that the optical pick-up device 1 has been moved to theinitial position. This initial position detecting switch is adapted sothat each of optical axes P₁, P₂ of the first and second object lenses7, 8 of the optical pick-up device 1 is moved up to the innermostcircumferential side where it is located at lead-in position 2a or 2b ofthe first or second optical disc 210 or 211 loaded on the disc table 4,the initial position detecting switch is caused to undergo pressingoperation by a portion of the optical pick-up device 1 to detect thatthe optical pick-up device 1 has reached the read-out starting positionof the first or second optical disc 210 or 211.

In the case where the reproduction mode is selected in the optical discrecording and/or reproducing apparatus, when the optical pick-up device1 is caused to undergo feed operation in the direction indicated byarrow X₂ in FIG. 2 and it is detected by the initial position detectingswitch that it has been made to the initial position, the feed operationin the direction indicated by arrow X₂ in FIG. 2 is once stopped.Following this stop, the feed motor is driven in the forward rotationdirection so that the optical pick-up device 1 is caused to undergoconstant speed (velocity) feed in the direction indicated by arrow X₁ inFIG. 2. As a result, read-out operation of information signals recordedon the first or second optical disc 210 or 211 is carried out. Thus,those information signals are reproduced.

In accordance with the optical disc recording and/or reproducingapparatus using the optical pick-up device 1 according to thisinvention, since it is possible to respectively detect, withoutnecessity to respectively initial position detecting switches incorrespondence with the first and second object lenses 7, 8, respectivelead-in position 2a, 2b of the first or second optical disc 210 or 211of the first and second object lenses 7, 8 by the single initialposition detecting switch, the number of parts can be reduced.

The first object lens 7 and the second object lens 8 disposed at theabove-described optical pick-up device 1 are attached on the bobbin 9 sothat respective optical axes P₁, P₂ are located at respective lead-inpositions 2a, 2b of the first and second optical discs 210, 211. In thecase where positions of the first object lens 7 and the second objectlens 8 are set in order to become in correspondence with the firstoptical disc 210 and the second optical disc 211 in which distances fromthe rotation center O₁ up to the lead-in positions 2a, 2b are differentfrom each other as stated above, when distance from the rotation centerO₁ up to the lead-in position 2a of the first optical disc 210 isassumed to be R₁ mm and distance from the rotation center O₁ up to thelead-in position 2b of the second optical disc 211 is assumed to be R₂mm, if distance between respective optical axes P₁, P₂ of the firstobject lens 7 and the second object lens 8 is 2d mm,

    R.sub.2.sup.2 =R.sub.1.sup.2 +(2d).sup.2                   (1)

d is selected so as to satisfy the above-mentioned equation (1), wherebywhen the optical pick-up device 1 has reached the read starting positionof information signals of the innermost circumferential side, respectiveoptical axes P₁, P₂ of the first and second object lenses 7, 8 can bepositioned in correspondence with respective lead-in positions 2a, 2b ofthe first and second optical discs 210, 211.

Moreover, while the second object lens 8 is set so that its optical axisP₂ is located at the lead-in position 2b of the second optical disc 211in the state where the optical axis P₁ of the first object lens 7 islocated at the lead-in position 2a of the first optical disc 210,setting may be made such that its optical axis P₂ is located at anyother lead-in position within TOC (Table of Contents) provided at theinner circumferential side of the second optical disc 211 similarly tothe first object lens 7 as occasion demands.

The operation for reproducing information signals recorded on the firstor second optical disc 210 or 211 by using the optical disc recordingand/or reproducing apparatus provided with the optical pick-up device 1constituted as described above will now be described.

Initially, in the case of reproducing the first optical disc 210, thefeed motor is driven to allow the optical pick-up device 1 to undergofeed operation toward the inner circumferential side of the firstoptical disc 210 in the direction indicated by arrow X₂ in FIG. 2. Whenthe optical pick-up device 1 is caused to undergo feed operation in thedirection indicated by arrow X₂ in FIG. 2 and the initial positiondetecting switch is caused to undergo pressing operation by the opticalpick-up device 1, it is detected that the optical axis P₁ of the firstobject lens 7 is located at the lead-in position 2a of the first opticaldisc 210. Thus, drive of the feed motor is once stopped. Following stopof this feed motor, the feed motor is driven in the forward rotationdirection. As a result, the optical pick-up device 1 is caused toundergo feed operation in the direction indicated by arrow X₁ in FIG. 2toward the outer circumferential side of the first optical disc 210 toscan the signal recording area of the first optical disc 210 by lightbeams emitted from the optical pick-up device 1 and focused by the firstobject lens 7 to detect return light beams reflected from the firstoptical disc 210 by light detector within the optical pick-up device.Thus, reproduction of information signals recorded on the first opticaldisc 210 is carried out.

Moreover, also in the case of reproducing the second optical disc 211,the feed motor is driven to allow the optical pick-up device 1 toundergo feed operation toward the inner circumferential side of thesecond optical disc 211 in the direction indicated by arrow X₂ in FIG. 2until the optical pick-up device 1 pushes the initial position detectingswitch to once stop drive operation of the feed motor when the opticalaxis P₂ of the second object lens 8 is located at the lead-in position2b of the second optical disc 211. Following stop of the feed motor,this feed motor is driven in the forward rotation direction to allow theoptical pick-up device 1 to undergo feed operation in the directionindicated by arrow X₁ in FIG. 2 toward the outer circumferential side ofthe second optical disc 211. At this time, the signal recording area ofthe second optical disc 211 is scanned by light beams emitted from theoptical pick-up device 1 and focused by the second object lens 8 todetect return light beams reflected from the second optical disc 211 bylight detector within the optical pick-up device. Thus, reproduction ofinformation signals recorded on the second optical disc 211 is carriedout.

As described above, since the optical pick-up device 1 of the firstembodiment is attached on the bobbin 9 so that when the optical pick-updevice 1 is positioned at the innermost circumferential side of thefirst or second optical disc 210 or 211, the optical axis P₁ of thefirst object lens 7 is located at the lead-in position 2a of the firstoptical disc 210 and the optical axis P₂ of the second object lens 8 islocated at the lead-in position 2b of the second optical disc 211, theoptical pick-up device 1 can detect lead-in positions 2a, 2b at the sameposition with respect to two kinds of first and second optical discs210, 211 different in the specification where lead-in positions 2a, 2bare different from each other. For this reason, movement control to theinformation signal read starting position of the optical pick-up device1 is facilitated. As a result, various parts such as initial positiondetecting switch, etc. can be reduced. Thus, the manufacturing cost canbe reduced.

Moreover, since this optical pick-up device 1 is attached on the bobbin9 so that the optical axis P₁ of the first object lens 7 is located atthe lead-in position 2a of the first optical disc 210 and the opticalaxis P₂ of the second object lens 8 is located at the lead-in position2b of the second optical disc 211, when read operation of informationsignals respectively recorded on the two kinds of first and secondoptical discs 210, 211 different in the specification where lead-inpositions 2a, 2b are different from each other is started, the first andsecond object lenses 7, 8 are caused to undergo drive displacement bythe same electromagnetic drive mechanism 10 in the state where switchingbetween reference positions is not carried. For this reason, themechanism for carrying out the focusing control and the tracking controlof the first and second object lenses 7, 8 can be simplified. Thus,miniaturization and light weight of the optical pick-up device 1 itselfcan be realized.

Further, since the above-described optical pick-up device 1 uses theobject lens drive unit of the so-called shaft slide rotatable type, thefirst and second object lenses 7, 8 can be arranged in a well-balancedmanner with the support shaft 11 being as center. For this reason, thisobject lens arrangement can also function as the so-called counterbalance in which one object lens serves as weight for balance of theother object lens. Accordingly, it becomes unnecessary to providecounter balance with respect to the first and second object lenses 7, 8.Thus, miniaturization and light weight of the entirety of the device canbe realized.

Further, since the second object lens 8 moving on the line S₁ passingthrough the rotation center O₁ of the second optical disc 211 is adaptedso that inclination of recording tracks is not changed in dependencyupon position of the optical pick-up device 1, there results lessdisplacement quantity of the second object lens 8 with respect to thetangential direction of the second optical disc 211. Accordingly, thissecond object lens 8 is not caused to undergo restriction in settingdetection method for information signal. As a result, the degree offreedom of setting is great.

It is to be noted that while the above-described optical pick-up device1 is constituted so that the bobbin 9 on which the first and secondobject lenses 7, 8 are attached is rotated with the support shaft 11being as center, there may be also employed a configuration such thatthe bobbin 9 is supported at the front end sides of plural elasticsupporting members in linear form of which base end sides are supportedat the fixed portion so that the first and second object lenses 7, 8attached on the bobbin 9 are caused to undergo drive displacement in adirection in parallel to their optical axes and in a directionperpendicular to the optical axes.

Moreover, while the optical pick-up device 1 according to the firstembodiment is set so that when it is moved to the read starting positionof information signal, respective optical axes P₁, P₂ of the first andsecond object lenses 7, 8 are in correspondence with respective lead-inpositions of CD and DVD, it is a matter of course that the opticalpick-up device 1 may be set in correspondence with other optical disc,e.g., video disc, etc. In addition, the optical pick-up device 1 may beof structure in which third object lens corresponding to third opticaldisc is provided as occasion demands.

In this example, as the first and second object lenses 7, 8 used in theoptical pick-up device 1, there is used object lenses having numericalaperture NA in conformity with the recording density of the first andsecond optical discs 210, 211. As the second object lens 8 used forrecording and/or reproduction of the second optical disc 211 in whichhigh density recording of information signals has been realized, thereis used object lens having great numerical aperture NA as compared tothe first object lens 7.

The second embodiment of the optical pick-up device according to thisinvention and an optical disc player using such optical pick-up devicewill now be described.

Similarly to the previously described optical pick-up device 1 of thefirst embodiment, optical pick-up device 21 disclosed here is also usedfor recording and/or reproduction of Compact Disc (CD) which is thefirst optical disc having diameter caused to be 120 mm and thicknesscaused to be 1.2 mm and adapted so that sound signals are mainlyrecorded, and Digital Video Disc (DVD) which is the second optical disc211 in which two optical discs each having diameter caused to be 120 mmand thickness of the disc substrate caused to be 0.6 mm are stucktogether so that the entire thickness becomes equal to 1.2 mm andadapted so that information signals such as video signals, etc. aremainly recorded at higher density as compared to the first optical disc210.

The optical pick-up device 21 of the second embodiment is used in, e.g.,optical disc recording and/or reproducing apparatus using theabove-described first and second optical discs 210, 211 as recordingmedium, and is disposed within the optical disc recording and/orreproducing apparatus through a base 23 constituting the apparatus bodyas shown in FIG. 5. On this base 23, the first or second optical disc210 or 211 is loaded, and a disc rotational operation mechanism composedof a disc table 24 for allowing these optical discs 210, 211 toselectively undergo rotational operation and spindle motor forrotationally driving this disc table 24 is disposed. The spindle motorconstituting this disc rotational operation mechanism is attached at thelower surface side of the base 23.

Moreover, on the base 23, a guide shaft 25a and a drive shaft 25b aredisposed in parallel to each other in the state where the disc table 24is put therebetween. The optical pick-up device 21 is movably supportedin the radial direction of the first or second optical disc 210 or 211loaded on a disc table 24 by allowing both ends of an optical block 26including therewithin light detector for detecting light beams fromsemiconductor laser serving as a light source or light beams reflectedfrom the first or second optical disc 210 or 211 to carry out readoperation of information signals recorded on these optical discs 210,211 and optical parts such as beam splitter, etc. to be supported by theguide shaft 25a and the drive shaft 25b. Further, the optical pick-updevice 21 is adapted so that when the drive shaft 25b is rotationallydriven by feed motor (not shown), it is caused to undergo feed operationin the direction indicated by arrow X₁ and in the direction indicated byarrow X₂ in FIG. 5 which are tracking direction extended in (along) theradial direction of the first or second optical disc 210 or 211 loadedon the disc table 24 while being guided by the guide shaft 25a.

In this example, the optical pick-up device 21 is adapted so that in thecase of carrying out read-out operation of information signals recordedon the first or second optical disc 210, 211, it is caused to undergofeed operation in the direction indicated by arrow X₁ in FIG. 5 towardthe outer circumferential side of the first or second optical disc 210or 211 from the lead-in position provided at the inner circumferentialside of the first or second optical disc 210 or 211.

This optical pick-up device 21 comprises, as shown in FIGS. 5 and 6, afirst object lens 27 used at the time of reading out information signalsrecorded on the first optical disc 210, a second object lens 28 used atthe time of reading out information signals recorded on the secondoptical disc 211, and a bobbin 29 on which these first and second objectlenses 27, 28 are attached. The first and second object lenses 27, 28are attached on the bobbin 29 so that respective optical axes are inparallel to each other.

As shown in FIG. 6, this bobbin 29 is formed so as to take rectangularshape, and is adapted so that the first and second object lenses 27, 28are attached thereon in parallel in the length direction. The bobbin 29is adapted so that its bottom end portion is fixed on a fixed portion 31provided on a supporting pedestal (base) 30 attached on the opticalblock 26, and both sides opposite to each other in the length directionthereof are supported by plural elastic supporting members 31a, 31b and32a, 32b which take linear form, extended in the direction substantiallyperpendicular to the optical axes of the first and second object lenses27, 28, whereby the bobbin 29 is movably supported in the focusingdirection which is the first direction in parallel to the optical axesof the first and second object lenses 27, 28 and in the trackingdirection which is the second direction perpendicular to the opticalaxes of the first and second object lenses 27, 28.

The plural elastic supporting members 31a, 31b and 32a, 32b for movablysupporting the bobbin 29 are formed by metallic material in a linearform having elasticity such as phosphor bronze, etc. Further, as shownin FIG. 6, the bobbin 29 is adapted so that front end portions of theelastic supporting members 31a, 31b and 32a, 32b are fixed with respectto supporting projections 33, 34 provided in a projected manner(hereinafter simply referred to as "projected" as occasion may demand)at both sides opposite to each other in the length direction where thefirst and second object lenses 27, 28 are juxtaposed, whereby the bobbin29 is movably supported in the focusing direction of the direction inparallel to the optical axes of the first and second object lenses 27,28 and in the tracking direction of the direction perpendicular to theoptical axes of the first and second object lenses 27, 28.

Further, the bobbin 29 cantilever-supported by the elastic supportingmembers 31a, 31b and 32a, 32b of which base end portions are fixed onthe fixed portion 31 are caused to undergo drive displacement in thefocusing direction of the direction in parallel to the optical axes ofthe first and second object lenses 27, 28 and in the tracking directionof the direction perpendicular to the optical axes of the first andsecond object lenses 27, 28 by an electromagnetic drive mechanism 35.

Namely, by the elastic supporting members 31a, 31b and 32a, 32b whichsupport the bobbin 29 and the electromagnetic drive mechanism 35, thedrive mechanism for allowing the first and second object lenses 27, 28to undergo drive displacement in two directions of the focusingdirection and the tracking direction perpendicular to each other isconstituted.

As shown in FIG. 6, the electromagnetic drive mechanism 35 whichconstitutes the drive mechanism for the first and second object lenses27, 28 comprises drive coils 40, 41 for focusing wound so as to takerectangular tubular shape, which are respectively attached at openingportions 38, 39 formed at both sides opposite to each other in thelength direction of the bobbin 29, drive coils 42a, 42b and 43a, 43b fortracking wound so as to take flat plate rectangular shape, which areattached by respective one pairs at one side surface of these focusingdrive coils 40, 41, a pair of magnets 44, 45 disposed in a manneropposite to these coils 40, 41, 42a, 42b, 43a, 43b, and yokes 46, 47 soas to take U-shape, which support these magnets 44, 45. These yokes 46,47 are formed by raising a portion of the fixed portion 31 consisting ofmagnetic material. Further, as shown in FIG. 6, the respective magnets44, 45 are attached, by using adhesive agent, etc. at the surface sideopposite to the focusing drive coils 40, 41 and the tracking drive coils42a, 42b and 43a, 43b of one pieces 46a, 47a of the respective yokes 46,47. In this example, other pieces 46b, 47b of the respective yokes 46,47 are inserted into the focusing drive coils 40, 41 to take tubularshape, which are attached on the bobbin 29, and are opposed to themagnets 44, 45.

When drive current corresponding to focusing error signal is deliveredto the focusing drive coils 40, 41 of the electromagnetic drivemechanism 35 having such configuration, the bobbin 29 is caused toundergo drive displacement in the direction in parallel to the opticalaxes of the first and second object lenses 27, 28 by action of thisdrive current and magnetic flux from the magnets 44, 45. Thus, focusingcontrol of the first and second object lenses 27, 28 is carried out.Moreover, when drive current corresponding to tracking error signal isdelivered to the tracking drive coils 42a, 42b and 43a, 43b, the bobbin29 is caused to undergo drive displacement in the directionperpendicular to the optical axes of the first and second object lenses27, 28 by action of this drive current and magnetic flux from themagnets 44, 45. Thus, tracking control of the first and second objectlenses 27, 28 is carried out.

Further, within the optical block 26 of the optical pick-up device 21,there are included first semiconductor laser serving as a first lightsource to emit first light beams, which is used for carrying outrecording and/or reproduction of the first optical disc 210, and secondsemiconductor laser serving as a second light source to emit secondlight beams, which is used for carrying out recording and/orreproduction of the second optical disc 211 in which high densityrecording of information signals has been realized.

In this case, as the first semiconductor laser, there is usedsemiconductor laser adapted for emitting light beams having wavelengthof 780±10 nm. As the second semiconductor laser, there is providedsemiconductor laser adapted for emitting light beams having wavelengthof 680 nm or less.

Within the optical block 26, there are provided a first optical system51 for guiding first light beams emitted from the first semiconductorlaser to the first object lens 27 and for guiding return light beamsreflected from the first optical disc 210 and incident through the firstobject lens 27 to light detector constituted by photo-detector, etc.,and a second optical system 52 for guiding second light beams emittedfrom the second semiconductor laser to the second object lens 28, andfor guiding return light beams reflected from the second optical disc211 and incident through the second object lens 28 to light detectorconstituted by photo-detector, etc.

The first optical system 51 is constituted by optical parts such ascollimator lens for allowing light beams emitted as divergent light fromthe first semiconductor laser to be parallel light, beam splitter forcarrying out separation between light beams emitted from the firstsemiconductor laser and return light beams reflected from the firstoptical disc 210, reflection mirror for reflecting light beams emittedfrom the first semiconductor laser which have been passed through thebeam splitter so as to allow them to be incident to the first objectlens 27, and for reflecting return light beams reflected from the firstoptical disc 210 and incident through the first object lens 27 so as toallow them to be incident to the beam splitter, and the like.

Moreover, the second optical system 52 is constituted, in a mannersimilar to the above, by optical parts such as collimator lens forallowing light beams emitted as a divergent light from the secondsemiconductor laser to be parallel light, beam splitter for carrying outseparation between light beams emitted from the second semiconductorlaser and return light beams reflected from the second optical disc 211,reflection mirror for reflecting light beams emitted from the secondsemiconductor laser which have been transmitted through the beamsplitter so as to allow them to be incident to the second object lens28, and for reflecting return light beams reflected from the secondoptical disc 211 and incident through the second object lens 28 so as toallow them to be incident to the beam splitter, and the like.

As shown in FIG. 6, the optical pick-up device 21 constituted asdescribed above is attached on the base 23 in the state supported by theguide shaft 25a and the drive shaft 25b in such a manner that lineconnecting respective optical axes P₁, P₂ of the first and second objectlenses 27, 28 is in parallel to tangential line L of recording track T₁formed in a concentrical form or in a spiral form with the rotationcenter O₁ being as center at the first or second optical disc 210 or 211loaded on the disc table 24. At this time, the optical pick-up device 21is attached on the base 23 in such a manner that the optical axis P₂ ofthe second object lens 28 used for recording and/or reproduction of thesecond optical disc 211 in which higher density recording has beenrealized is located on the line M passing through the rotation center O₁of the first or second optical disc 210 or 211 on the disc table 24.

As described above, since the optical pick-up device 21 of the secondembodiment is disposed on the base 23 in such a manner that the opticalaxis P₂ of the second object lens 28 is located on line M passingthrough the rotation center O₁ of the first or second optical disc 210,211, the first object lens 27 is placed so that the optical axis P₁placed at the position shifted from onto the line M passing through therotation center O₁ of the first or second optical disc 210 or 211. Forthis reason, in the case where the optical pick-up device 21 is causedto undergo feed operation in the direction indicated by arrow X₁ in FIG.5 to carry out recording and/or reproduction of information signals withrespect to the first optical disc 210 by using the first object lens 27,the optical axis P₁ of the first object lens 27 is shifted (deviates)from the center of the recording track of the first optical disc 210.For this reason, in the case of carrying out recording and/orreproduction of information signals with respect to the first opticaldisc 210 by using the object lens 27, the so-called push-pull method isemployed in tracking control to conduct a control such that light beamirradiated onto the first optical disc 210 through the first object lens27 is located on the recording track.

This push-pull method is a method in which single light beam is used toobtain tracking error signal, and is a method of detecting single returnlight beam reflected from the first optical disc 210 by bisected light(photo) detector to determine difference between detection outputsobtained from the divided respective light detectors (detector elements)to thereby obtain tracking error signal which is deviation componentwith respect to the recording track of light beam.

As this push-pull method, there may be employed a method as described inU.S. Pat. No. 4,491,940.

On the other hand, the second object lens 28 is adapted so that itsoptical axis P₂ is positioned on the line M passing through the rotationcenter O₁ of the first or second optical disc 210 or 211. For thisreason, in the case of carrying out recording and/or reproduction ofinformation signals with respect to the second optical disc 211 by usingthe second object lens 28, the optical axis P₂ of the second object lens28 is positioned on the center of the recording track of the secondoptical disc 211. In view of the above, in the tracking control in thecase of carrying out recording and/or reproduction of informationsignals with respect to the second optical disc 211 by using the secondobject lens 28, three-beam method may be used in addition to theabove-described push-pull method.

This three-beam method is a method of dividing single light beam emittedfrom the second semiconductor laser into single main beam and twosub-beams by using diffraction grating, etc. to irradiate two sub-beamsat portions before and after the main beam irradiated onto the center ofthe recording track to detect sub-beams disposed before and after themain beam by respective light detectors to determine difference betweendetection outputs obtained from the respective light detectors tothereby obtain tracking error signal which is deviation component withrespect to the recording track of the main beam.

As a device for obtaining tracking error signal by using the three-beammethod, there may be used a device as described in the Japanese PatentPublication No. 13123/1978.

Further, in the optical pick-up device 21 of the second embodiment, inthe focus control to conduct a drive control of the first or secondobject lens 27 or 28 in the optical axis direction thereof so that lightbeams emitted from the first or second light source are focused on thesignal recording surface of the first or second optical disc 210 or 211,the so-called astigmatism method is used. This astigmatism method is amethod of detecting return light beam reflected from the first or secondoptical disc 210 or 211 by quadrisected light detector through, e.g.,cylindrical lens to determine sum of detection outputs obtained from therespective detectors and/or difference therebetween to thereby obtainfocus error signal which in-focus deviation component with respect tothe signal recording surface of light beam.

As a device for obtaining focus error signal by this astigmatism method,there is used a device as described in the U.S. Pat. No. 4,023,033.

The tracking error signal obtained by a detection method as describedabove is delivered to tracking drive coils 42a, 42b and 43a, 43b of theelectromagnetic drive mechanism 35. Thus, tracking control of the firstand second object lenses 27, 28 is carried out. Moreover, the focuserror signal is delivered to the focusing drive coils 40, 41. Thus,focusing control of the first and second object lenses 27, 28 is carriedout.

The optical pick-up device 21 is adapted so that light source used isswitched in dependency upon the first or second optical disc 210 or 211loaded into the optical disc recording and/or reproducing apparatus. Forthis reason, in the optical disc recording and/or reproducing apparatususing this optical pick-up device 21, there is provided a discriminationmechanism for discriminating whether loaded optical disc is the firstoptical disc 210 or the second optical disc 211 to switch ON/OFF of thelight source, i.e., drive of first or second semiconductor laser independency upon the discrimination result.

Since discrimination means described in the specification and thedrawings of the U.S. patent application Ser. No. 08/694,544 is used asthe above-mentioned discrimination mechanism, the description of thespecification and the drawings is applied thereto and their detaileddescription is omitted.

For better understanding of this discrimination mechanism, outlinethereof will be described below. This discrimination mechanism serves tocarry out discrimination between the first and second optical discs 210,211 in which track pitches are different from each other by utilizingthe fact that when light is irradiated onto the first or second opticaldisc 210 or 211 loaded into the optical disc recording and/orreproducing apparatus, diffusion angle of diffracted light of the 1-storder diffracted light or diffracted light of the order higher than thatwhich are diffracted by recording tracks formed at the first or secondoptical disc 210, 211 varies in dependency upon the pitch of therecording track, and comprises light source such as LED, etc. forirradiating light onto the first or second optical disc 210 or 211, andtwo light receiving elements corresponding to the first and secondoptical discs 210, 211 for receiving either one of rays of diffractedlight of the 1-st diffracted light and diffracted light of the orderhigher than that which are diffracted by recording tracks formed at thefirst or second optical disc 210 or 211. These light receiving elementsare disposed at the positions corresponding to diffusion angles of raysof diffracted light corresponding to the pitches of the recording tracksrespectively formed at the first and second optical discs 210, 211 andserve to discriminate by the light receiving signal whethercorresponding optical disc is the first optical disc 210 or the secondoptical disc 211.

In this example, the pitch of the recording track of the second opticaldisc 211 in which high density recording has been realized issufficiently smaller than that of the first optical disc 210.

The optical disc recording and/or reproducing apparatus using theoptical pick-up device 21 constituted as described above is adapted sothat the first and second object lenses 27, 28 are arranged in parallelin the direction of the tangential line L of recording tracks of thefirst or second optical disc 210 or 211, whereby, in reproducinginformation signals from any one of the first and second optical discs210, 211 in which thicknesses of their disc bases (substrates) aredifferent from each other, the first and second object lenses 27, 28 aredriven in the focusing direction and in the tracking direction by thecommon drive mechanism without switching the reference position. Forthis reason, the configuration of the optical pick-up device 21 can besimplified, and miniaturization and light weight of the optical pick-updevice 21 can be realized.

Moreover, in accordance with the optical pick-up device 21, it ispossible to independently use the first or second semiconductor laser,the first or second optical system 51, 52 and the first or second objectlens 27, 28 in correspondence with any one of the first and secondoptical discs 210, 211 in which thicknesses of their disc substrates aredifferent from each other. Accordingly, it is possible to use thecomponents respectively optimum in correspondence with the first andsecond optical discs 210, 211. Thus, optimization can be made also withrespect to optical discs having high wavelength dependency.

Accordingly, also with respect to the first and second object lenses 27,28, there are used object lenses of numerical apertures NA which arerespectively in conformity with the first and second optical discs 210,211.

An optical pick-up device 61 of the third embodiment according to thisinvention will now be described. This optical pick-up device 61 is alsoused in, e.g., optical disc recording and/or reproducing apparatus usingthe previously described first and second optical discs 210, 211 asrecording medium, and comprises, as shown in FIG. 7, a first object lens62 used at the time of reading out information signals recorded on thefirst optical disc 210, a second object lens 63 used at the time ofreading out information signals recorded on the second optical disc 211,and a bobbin 64 on which these first and second object lenses 62, 63 areattached. This bobbin 64 is slidable, with respect to a support shaft 66of which central portion is vertically provided on a supporting base(substrate) 65, in the axial direction of the support shaft 66, and isrotatably supported in a direction around the axis of the support shaft66. In addition, the first and second object lenses 62, 63 are attachedat bilateral symmetrical positions with the support shaft 66 of thebobbin 64 being as center so that respective optical axes P₁, P₂ are inparallel to each other.

With respect to the first and second object lenses 62, 63, the bobbin 64is slid in the axial direction of the support shaft 66, whereby focusingcontrol with respect to the first or second optical disc 210 or 211 iscarried out. As a result, the bobbin 64 is rotated with the supportshaft 66 being as center. Thus, tracking control with respect torecording tracks of the first or second optical disc 210 or 211 iscarried out.

Slide in the axial direction of the support shaft 66 of the bobbin 64and rotation with the support shaft 66 being as center are carried outby an electromagnetic drive mechanism 67. This electromagnetic drivemechanism 67 is composed of a focusing drive coil 68 wound on thecircumferential surface of a tubular portion 64a inserted through thesupport shaft 66 of the bobbin 64, a pair of tracking drive coils 69, 69disposed on the outer circumferential surface of the bobbin 64, a pairof focusing magnets 70, 70 disposed in a manner opposite to the focusingdrive coil 68, a pair of tracking magnets 71, 71 disposed in a manneropposite to respective tracking drive coils 69, 69, focusing yokes 72,72 formed in a rising manner (hereinafter simply referred to as"rising-formed" as occasion may demand) from the supporting base(substrate) 65 formed by magnetic material, which respectively supportthese magnets 71, 71, and tracking yokes 73, 73.

Moreover, also in the optical pick-up device 61 of the third embodiment,similarly to the above-described optical pick-up device 21 of the secondembodiment, within the optical block disposed at the lower surface sideof the supporting base 65 on which the bobbin 64 on which the first andsecond object lenses 62, 63 are attached is movably supported, there areincluded first semiconductor laser serving as a first light source toemit first light beams, which is used for carrying out recording and/orreproduction of the first optical disc 210, and second semiconductorlaser serving as a second light source to emit second light beams, whichis used for carrying out recording and/or reproduction of the secondoptical disc 211 in which high density recording of information signalshas been realized.

In this case, as the first semiconductor laser, there is usedsemiconductor laser adapted to emit light beams of wavelength of 780±10nm. As the second semiconductor laser, there is used semiconductor laseradapted to emit light beams of wavelength of 680 nm or less.

Within the optical block, there are provided a first optical system forguiding first light beams emitted from the first semiconductor laser tothe first object lens 62 and for guiding return light beams reflectedfrom the first optical disc 210 and incident through the first objectlens 62 to light detector constituted by photo-detector, etc., and asecond optical system for guiding second light beams emitted from thesecond semiconductor laser to the second object lens 63 and for guidingreturn light beams reflected from the second optical disc 211 andincident through the second object lens 63 to light detector constitutedby photo-detector, etc.

Since the first and second optical systems provided at this opticalpick-up device 61 is of the configuration similar to those provided atthe previously described optical pick-up device, detailed explanation isomitted.

As shown in FIG. 7, the optical pick-up device 61 constituted asdescribed above is disposed within the player body in such a manner thatline connecting respective optical axes P₁, P₂ of the first and secondobject lenses 62, 63 is in parallel to tangential line L of recordingtrack T₁ formed in a concentrical form or in a spiral form, with therotation center O₁ being as center, at the first or second optical disc210 or 211 loaded on the disc table of the optical disc recording and/orreproducing apparatus. At this time, the optical pick-up device 61 isdisposed within the player body in such a manner that the optical axisP₂ of the second object lens 63 used for recording and/or reproductionof the second optical disc 211 in which high density recording has beenrealized is located on the line M passing through the rotation center O₁of the first or second optical disc 210 or 211 on the disc table.

Also in this optical pick-up device 61, similarly to the previouslydescribed optical pick-up device 21 of the second embodiment, in thecase where the first object lens 62 is used to carry out recordingand/or reproduction of information signals with respect to the firstoptical disc 210, tracking control using the push-pull method is carriedout. In the tracking control in the case where the second object lens 63is used to carry out recording and/or reproduction of informationsignals with respect to the second optical disc 211, the three-beammethod is used in addition to the above-described push-pull method.Moreover, in the focus control to drive and control the first or secondobject lens 62 or 63 in the optical axis direction thereof, theso-called astigmatism method is used.

In addition, in the optical disc recording and/or reproducing apparatususing this optical pick-up device 61, similarly to the previouslydescribed optical disc recording and/or reproducing apparatus, there isprovided a discrimination mechanism for discriminating whether opticaldisc to be loaded is either the first optical disc 210 or the secondoptical disc 211 to switch, in dependency upon the discriminationresult, ON/OFF of the light source used, i.e., drive of the first orsecond semiconductor laser.

Since the optical pick-up device 61 constituted as described above isadapted so that the first object lens 62 and the second object lens 63are disposed at positions symmetrical with the support shaft 66 being ascenter, one of the first and second object lenses 62, 63 acts as alsoweight for balance which is so called counter balance with respect tothe other. For this reason, it becomes unnecessary for this opticalpick-up device 61 to provide counter-balance with respect to the firstand second object lenses 62, 63. Thus, the entirety of the device can besmall-sized and can be lightened (in weight).

An optical pick-up device 81 of the fourth embodiment according to thisinvention will now be described with reference to FIG. 8. Since thisoptical pick-up device 81 has configuration substantially similar tothat of the previously described optical pick-up device of the secondembodiment shown in FIGS. 5 and 6, the same reference numerals arerespectively attached to the same members and the detailed descriptionthereof will be omitted.

As shown in FIG. 8, this optical pick-up device 81 is attached on acanti-lever supported bobbin 85 in such a manner that respective opticalaxes P₁, P₂ of the first object lens 82 and the second object lens 83are located on the line M passing through the rotation center O₁ of thefirst or second optical disc 210 or 211 loaded on the disc table of theoptical disc recording and/or reproducing apparatus, i.e., arejuxtaposed in the tracking direction of the first or second optical disc210 or 211.

Since the optical pick-up device 81 constituted in this way permitsrespective optical axes P₁, P₂ of the first object lens 82 and thesecond object lens 83 to be located at the center of recording track ofthe first or second optical disc 210 or 211, even in the case wereeither object lens 82 or object lens 83 is used, it is possible to scanthe recording tracks by light beams with high accuracy. Accordingly,recording/reproduction of information signals can be carried out withsatisfactory recording/reproduction characteristic at all times.

While the above-described respective optical pick-up devices are causedto be of the structure comprising the first and second object lenses incorrespondence with CD and DVD, they may be caused to be of thestructure comprising third object lens in order to cope with any otheroptical disc as occasion demands. This optical pick-up device is causedto be, e.g., of structure in which the first object lens is disposed inthe state positioned on the line passing through the center of theoptical disc, the first to third object lenses are juxtaposed in thetangential direction of the recording tracks of the optical disc, andthe second and third object lenses are respectively disposed atsymmetrical positions with respect to the optical axis of the firstobject lens.

Industrial Applicability

As described above, the optical pick-up device according to thisinvention comprises first object lens, second object lens havingnumerical aperture different from numerical aperture of the first objectlens, bobbin on which the first and second object lenses are attached,and drive mechanism for moving the bobbin in the first direction inparallel to the optical axes of the first and second object lenses andin the second direction perpendicular to the optical axes of the firstand second object lenses to selectively use the first and second objectlenses, thereby permitting recording and/or reproduction of at least twokinds of optical discs different in kind. Accordingly, it is possible tocarry out, by using single optical pick-up device, recording and/orreproduction of information signals with respect to optical discs ofplural specifications.

Particularly, since one object lens is adapted so that its optical axisis caused to be positioned on the line passing through the center of theoptical disc, even if corresponding optical disc is optical disc havingsmall track pitch which permits high density recording, it becomespossible to carry out recording and/or reproduction of informationsignals with high accuracy.

In addition, since such approach is employed to allow the first andsecond object lenses to undergo drive control in the focusing directionand/or in the tracking direction by the common drive mechanism,miniaturization and thin thickness structure of the device itself can berealized.

We claim:
 1. An optical pick-up device for recording and/or reproductionof at least two kinds of optical discs, the optical pick-up devicecomprising:a first object lens; a second object lens; a bobbin attachedin such a manner that respective optical axes of the first and secondobject lenses are in parallel to each other, and either one of the firstand second object lenses is disposed on a line passing through thecenter of an optical disc; and a drive mechanism for moving the bobbinin a first direction in parallel to the optical axes of the first andsecond object lenses and in a second direction perpendicular to theoptical axes, wherein the first and second object lenses are attached onthe bobbin such that when the object lens disposed on the line isdisposed at the innermost circumference of a first kind of optical disc,that object lens is located at a read position of the first kind ofoptical disc and the other object lens is disposed at a positioncorresponding to the read position of a second kind of optical disc. 2.The optical pick-up device of claim 1,wherein the first and secondobject lenses are attached on the bobbin along a tangential linedirection of tracks of the optical disc.
 3. An optical pick-up device asset forth in claim 2,wherein the drive mechanism comprises at least oneelastic supporting member for movably supporting the bobbin in the firstand second directions, a fixed portion on which the end portion of theelastic supporting member is attached, plural coils provided at eitherone of the bobbin and the fixed portion, and at least one magnetprovided at the other and opposite to the plural coils.
 4. An opticalpick-up device as set forth in claim 3,wherein the device furthercomprises a first light source, a first optical system for guiding lightbeams from the first light source to the first object lens, a secondlight source for emitting light beams having wavelength different fromwavelength of light beams emitted from the first light source, and asecond optical system for guiding light beams from the second lightsource to the second object lens.
 5. An optical pick-up device as setforth in claim 4,wherein numerical aperture of the first object lens andnumerical aperture of the second object lens are different from eachother.
 6. The optical pick-up device of claim 1,wherein the first andsecond object lenses are attached on the bobbin so that they arerespectively positioned on a line passing through the center of theoptical disc.
 7. An optical pick-up device as set forth in claim6,wherein the drive mechanism comprises at least one elastic supportingmember for movably supporting the bobbin in the first and seconddirections, a fixed portion on which the end portion of the elasticsupporting member is attached, plural coils provided at either one ofthe bobbin and the fixed portion, and at least one magnet provided atthe other and opposite to the plural coils.
 8. An optical pick-up deviceas set forth in claim 7,wherein the device further comprises a firstlight source, a first optical system for guiding light beams from thefirst light source to the first object lens, a second light source foremitting light beams having wavelength different from wavelength oflight beams emitted from the first light source, and a second opticalsystem for guiding light beams from the second light source to thesecond object lens.
 9. An optical pick-up device as set forth in claim8,wherein numerical aperture of the first object lens and numericalaperture of the second object lens are different from each other.
 10. Anoptical pick-up device for recording and/or reproduction of at least twokinds of optical discs,the optical pick-up device comprising: a firstobject lens; a second object lens having a numerical aperture differentfrom a numerical aperture of the first object lens; a bobbin attached insuch a manner that respective optical axes of the first and secondobject lenses are in parallel to each other, and at least one of thefirst and second object lenses is located at a starting position of anoptical disc when the optical pick-up device is positioned at theinnermost circumference of the optical disc; and a drive mechanism formoving the bobbin in a first direction in parallel to the optical axesof the first and second object lenses and in a second directionperpendicular to the optical axes, wherein the first and second objectlenses are attached on the bobbin in such a manner that when one objectlens is located is located at a starting position of an optical disc ofa first kind when the optical pick-up device is positioned at theinnermost circumference of the optical disc of a first kind, the otherobject lens is located at a position corresponding to the startingposition of an optical disc of a second kind.
 11. The optical pick-updevice of claim 10,wherein the first and second object lenses areattached on the bobbin in such a manner that when one object lensdisposed on a line passing through the center of the optical disc islocated at a read starting position of one kind of optical disc, theother object lens is located at a read starting position of another kindof optical disc.
 12. The optical pick-up device of claim 10,whereineither one of the first and second object lenses is disposed on a linepassing through the center of the optical disc.
 13. The optical pick-updevice of claim 10,wherein the drive mechanism comprises at least oneelastic supporting member for movably supporting the bobbin in the firstand second directions, a fixed portion on which the end portion of theelastic supporting member is attached, plural coils provided at eitherone of the bobbin and the fixed portion, and at least one magnetprovided at the other and opposite to the plural coils.
 14. An opticalpick-up device as set forth in claim 13,wherein the device furthercomprises a first light source, a first optical system for guiding lightbeams from the first light source to the first object lens, a secondlight source for emitting light beams having wavelength different fromwavelength of light beams emitted from the first light source, and asecond optical system for guiding light beams from the second lightsource to the second object lens.
 15. An optical pick-up device used forrecording and/or reproduction of at least two kinds of optical discshaving thicknesses different from each other,the optical pick-up devicecomprising: a first object lens for irradiating light beams from a firstlight source onto either one of the two kinds of optical discs; a secondobject lens for irradiating light beams from a second light source ontothe other of the two kinds of optical discs; a bobbin attached in such amanner that respective optical axes of the first and second objectlenses are in parallel to each other, and either one of the first andsecond object lenses is disposed on a line passing through the center ofan optical disc; and a drive mechanism for moving the bobbin in a firstdirection in parallel to the optical axes of the first and second objectlenses and in a second direction perpendicular to the optical axes,wherein the first and second object lenses are attached on the bobbinsuch that when the object lens disposed on the line is disposed at theinnermost circumference of a first kind of optical disc, that objectlens is located at a read position of the first kind of optical disc andthe other object lens is disposed at a position corresponding to theread position of a second kind of optical disc.
 16. An optical pick-updevice as set forth in claim 15,wherein the first and second objectlenses are attached on the bobbin along a tangential direction of tracksof the optical disc.
 17. An optical pick-up device as set forth in claim16,wherein the drive mechanism comprises at least one elastic supportingmember for movably supporting the bobbin in the first and seconddirections, a fixed portion on which the end portion of the elasticsupporting member is attached, plural coils provided at either one ofthe bobbin and the fixed portion, and at least one magnet provided atthe other and opposite to the plural coils.
 18. An optical pick-updevice as set forth in claim 17,wherein numerical aperture of the firstobject lens and numerical aperture of the second object lens aredifferent from each other.
 19. An optical pick-up device as set forth inclaim 15,wherein the first and second object lenses are attached on thebobbin so that they are respectively positioned on a line passingthrough the center of the optical disc.
 20. An optical pick-up device asset forth in claim 19,wherein the drive mechanism comprises at least oneelastic supporting member for movably supporting the bobbin in the firstand second directions, a fixed portion on which the end portion of theelastic supporting member is attached, plural coils provided at eitherone of the bobbin and the fixed portion, and at least one magnetprovided at the other and opposite to the plural coils.
 21. An opticalpick-up device as set forth in claim 20,wherein numerical aperture ofthe first object lens and numerical aperture of the second object lensare different from each other.
 22. A recording and/or reproducingapparatus for optical discs, which is adapted for carrying out recordingand/or reproduction of at least two kinds of optical discs havingthicknesses different from each other,the apparatus comprising: anoptical pick-up device comprising a first object lens for irradiatinglight beams from a first light source onto either one of the two kindsof optical discs, a second object lens for irradiating light beams froma second light source onto the other of the two kinds of optical discs;a bobbin on which the first and second object lenses are attached insuch a manner that respective optical axes thereof are in parallel toeach other, and either one of the first and second object lenses ispositioned on a line passing through the center of an optical disc, anda drive mechanism for moving the bobbin in a first direction in parallelto the optical axes of the first and second object lenses and in asecond direction perpendicular to the optical axes; and a discriminationmechanism for discriminating the kind of optical disc loaded into therecording and/or reproducing apparatus to carry out switching betweenthe first light source and the second light source on the basis of thediscrimination mechanism's discrimination result, wherein the first andsecond object lenses are attached on the bobbin such that when theobject lens disposed on the line is disposed at the innermostcircumference of a first kind of optical disc, that object lens islocated at a read position of the optical disc and the other object lensis disposed at a position corresponding to the read position of a secondkind of optical disc.
 23. The recording and/or reproducing apparatus ofclaim 22,wherein the first and second object lenses are attached on thebobbin along a tangential line direction of tracks of the optical disc.24. The recording and/or reproducing apparatus of claim 23,wherein thedrive mechanism comprises at least one elastic supporting member formovably supporting the bobbin in the first and second directions, afixed portion on which the end portion of the elastic supporting memberis attached, plural coils provided at either one of the bobbin and thefixed portion, and at least one magnet provided at the other andopposite to the plural coils.
 25. The recording and/or reproducingapparatus of claim 24,wherein the numerical aperture of the first objectlens and the numerical aperture of the second object lens are differentfrom each other.
 26. The recording and/or reproducing apparatus of claim23,wherein the first and second object lenses are attached on the bobbinso that they are respectively positioned on a line passing through thecenter of the optical disc.
 27. The recording and/or reproducingapparatus of claim 26,wherein the drive mechanism comprises at least oneelastic supporting member for movably supporting the bobbin in the firstand second directions, a fixed portion on which the end portion of theelastic supporting member is attached, plural coils provided at eitherone of the bobbin and the fixed portion, and at least one magnetprovided at the other and opposite to the plural coils.
 28. Therecording and/or reproducing apparatus of claim 27,wherein the numericalaperture of the first object lens and the numerical aperture of thesecond object lens are different from each other.